Salamanders have the remarkable ability to regenerate lost limbs. A key feature of limb regeneration is proliferation of stump cells in order to replace the lost parts. The initial stimulus for this proliferation is suggested to be products or cells released from nerves damaged by the amputation. In species whose limbs regenerate poorly or not at all, such as frogs, mice, and humans, very limited stump cell proliferation occurs. Many of the methods successfully used to enhance regeneration of such limbs add or stimulate nervous tissue. The research proposed here will test whether a cellular or a non-cellular component of peripheral nerve will stimulate proliferation when grafted into a limb stump which ordinarily would regenerate very poorly. Grafts will be derived from salamander dorsal root ganglia grown in tissue culture, and will consist of sensory neurons, neurites, myelin, or Schwann cells, or combinations of those. Data to be collected are: a) probability and rate of regeneration, b) mitotic and DNA synthetic activity in the stump, and c) quality of the skeletal pattern in the regenerate.